Nuclear arachidonic acid uptake and utilization

LAYERENZA, JUAN P; VES-LOSADA, ANA

Rosario

Congreso; XLII Reunión Anual de la SAIB; 2006

SAIB

Regulation of gene expression by fatty acids is an event that takes place inside the nuclei of eukaryotic cells, but the mechanisms of nuclear fatty acids (FA) uptake is still incompletely understood. We have already demonstrated that FA free or bound to L-FABP are incorporated into metabolic active nuclear lipids pools by an acyl-CoA pathway. In these experiments whole nuclei or isolated nuclear matrix (double membranedepleted nuclei) were incubated in vitro with [14C]FA. The aim of the present work was to determine if exogenous FA could be internalized to endonuclear lipids (nuclear matrix). With this purpose, nuclear 20:4n-6 pools were labeled by in vitro incubation of isolated nuclei from rat liver cells with [1-14C]20:4n-6, ATP and CoA at different times. After nuclear labeling, matrix were isolated removing the double nuclear membrane by incubation with 0.08% TX – 100. Arachidonic acid was incorporated in nuclear matrix lipid pools, as FFA and esterified to PL (PtdCho > PtdEtn > PtdIns) and neutral lipids (TAG >> DAG). These endonuclear 20:4n-6 pools could provide and endogenous source of PPARá – activating ligands, as FFA and / or through an in situ regulated PL hydrolysis. In conclusion, exogenous arachidonic acid not only is incorporated into nuclear membrane, but also is internalized to endonuclear lipid pools as FFA or esterified to PL and TAG. Regulation of gene expression by fatty acids is an event that takes place inside the nuclei of eukaryotic cells, but the mechanisms of nuclear fatty acids (FA) uptake is still incompletely understood. We have already demonstrated that FA free or bound to L-FABP are incorporated into metabolic active nuclear lipids pools by an acyl-CoA pathway. In these experiments whole nuclei or isolated nuclear matrix (double membranedepleted nuclei) were incubated in vitro with [14C]FA. The aim of the present work was to determine if exogenous FA could be internalized to endonuclear lipids (nuclear matrix). With this purpose, nuclear 20:4n-6 pools were labeled by in vitro incubation of isolated nuclei from rat liver cells with [1-14C]20:4n-6, ATP and CoA at different times. After nuclear labeling, matrix were isolated removing the double nuclear membrane by incubation with 0.08% TX – 100. Arachidonic acid was incorporated in nuclear matrix lipid pools, as FFA and esterified to PL (PtdCho > PtdEtn > PtdIns) and neutral lipids (TAG >> DAG). These endonuclear 20:4n-6 pools could provide and endogenous source of PPARa – activating ligands, as FFA and / or through an in situ regulated PL hydrolysis. In conclusion, exogenous arachidonic acid not only is incorporated into nuclear membrane, but also is internalized to endonuclear lipid pools as FFA or esterified to PL and TAG.